Separation using air flows of different velocities

ABSTRACT

An apparatus for separation of components having differing terminal velocities. The apparatus provides a substantially elongate, upwardly projected air flow acting to agitate, sort and separate the components according to a terminal velocity of each of the components. The apparatus also forms a bed of the components above the upwardly projected air flow and entrains a class of the components out of the bed.

FIELD OF THE INVENTION

This invention relates to an apparatus and method for effecting theseparation of items with different terminal velocities, such as sugarcane billets and leaf, as achieved in cane harvesters. In particular, itrelates to the use of air flows of differing velocities to separate leafand other trash from sugar cane billets.

BACKGROUND TO THE INVENTION

Various mechanisms are known whereby separations, such as the separationof billets of sugar cane from leaves, tops and other trash picked up bya harvester, are achieved. For sugar production it is desirable toefficiently separate sugar billets from other matter so as to deliver aclean product to sugar mills for crushing.

This separation has typically been attempted, albeit somewhatineffectively, in cane harvesters during harvest. In most knownarrangements a flow of air is drawn through the cane as it passesthrough the harvester. One such arrangement is described in AustralianPatent No. 569800 in the name of Claas OHG. This patent describes aseparation process wherein harvested cane is carried up an inclined beltconveyor. At the end of the conveyor the cane and other material fallsonto a transverse conveyor. Air is blown through the falling cane toseparate lighter material from the heavier cane billets. A suction fanis mounted above the conveyor belt to assist with ejection of theseparated material.

The Claas approach fails to achieve efficient separation at acceptableharvesting rates. Leaf is caught between cane billets and retained whilesome billets are discharged with leaf material. A more efficientapproach is required.

In other approaches air is drawn through a moving bed of cane toseparate cane billets from trash. Successful separation depends onutilising the difference in terminal velocity of a billet (typically 20m/s) and other inclusions to the harvested cane such as tops (typicalterminal velocity of 15 m/s) and leaves (typically 5 m/s). The usualconfiguration in a harvester is with a fan drawing air through the canebed. Commonly used fans do not provide a uniform velocity profile overthe whole treatment area. Uniformity of air flow is greatly affected bythe air inlet conditions and geometry of the chamber in which theseparation is effected and other factors including the presence andproperties of the cane bed itself. Consequently, such means ofseparating trash from cane billets have not proven efficient becausethey result in a loss of cane billets ejected with the trash from someparts of the treatment area and the retention of trash in other parts.

Another approach to cleaning trash from cane billets is a modificationof the Claas approach described above. A jet of air is blown through acurtain of falling cane to eject the trash. This configuration enablesbetter control over air velocity and hence improved efficiency ofseparation. However, there is still room for improvement in the qualityof the end product and in minimising loss of cane billets. Furthermore,the rate of processing must be increased to match the increase inharvesting speed with modern harvesters.

All of the above described methods cause a loss of cane when applied tobillets in a cane harvester, and additionally they fail to removesufficient extraneous matter. Cane is lost because it becomes entrainedwith leaf material or it is projected into the fan blades. Leaf can betrapped by the billets and not removed. Variation in density of the canebed can cause zones where the air velocity is impeded and reduced andthe effectiveness of the flow as a separation mechanism at these zonesis consequently reduced.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an apparatus andmethod to improve the efficiency and effectiveness of the separation ofobjects, items, components, and the like, into distinct classescharacterised by terminal velocity.

It is a further object of the invention to substantially ameliorate oneor more of the identified shortcomings in the known prior art.

Further objects will be evident from the following description.

DISCLOSURE OF THE INVENTION

In one aspect the present invention provides an apparatus for separationof components having differing terminal velocities, including means forproviding an upwardly projected air flow, said air flow acting toagitate, sort and separate said components according to a terminalvelocity of each of said components, means for forming a bed of saidcomponents above said upwardly projected air flow, means for entraininga class of said components out of the bed, said means for providing saidupwardly directed air flow including a narrow, elongate jet meansextending substantially across said bed of said components.

In one form of the invention the bed of components is formed byprojecting the components into and through the upwardly projectedairflow. In another form of the invention, the components aredistributed on a conveyor means which carries the components through theupwardly projected airflow.

In preference the apparatus further comprises a separation zone formedin the bed of components by the flow of air whereat components aredistributed according to terminal velocity with lower terminal velocitycomponents displaced upwardly with respect to higher terminal velocitycomponents.

The components may be definable in classes wherein each class has acharacteristic terminal velocity, and the terminal velocities of thecomponents in the class are distributed about a mean value which is thecharacteristic terminal velocity.

In preference the means for entraining a class of said components is alow speed fan drawing an entraining air flow away from the bed ofcomponents, said entraining air flow entraining low terminal velocitycomponents. The entraining air flow preferably acts throughout and/oradjacent the separation zone.

The upwardly projected flow of air and the entraining air flow actcooperatively to sort and segregate classes of components.

In preference the upwardly projected air flow has a velocity of between20 m/s and 60 m/s and preferably in the range 30 m/s and 50 m/s. Mostpreferably the velocity of the upwardly projected air flow is 40 m/s.

The entraining air flow preferably has a velocity of between 2 m/s and20 m/s. Most preferably the velocity of the entraining air flow is 12m/s.

In a second aspect the present invention is a self-propelled harvestercomprising cutting and gathering means at a forward end of theharvester; chopping means adjacent the cutting and gathering means forchopping harvested cane into billets and trash; means for projectingsaid billets and trash into a separation zone; separation means asdefined above providing at least one narrow, upwardly projected air flowthrough the separation zone, said air flow acting to agitate, sort andseparate the billets and trash, said entraining means entraining thetrash out of the separation zone.

In one form the chopping means and the means for projecting said billetsand trash into a separation zone are a single means such that thebillets and trash are projected into the separation zone immediatelyafter chopping.

The harvester may suitably include conveyor means adjacent theprojection means, said billets and trash forming a bed on the conveyormeans. In preference the conveyor means conveys the bed of billets andtrash through the upwardly projected air flow. The conveyor meanssuitably comprises a belt of open mesh material.

Alternatively, the projection means forms an unsupported bed in theseparation zone.

The means for entraining the trash out of the bed is suitably a lowspeed fan drawing an entraining air flow from the bed at a velocitysufficient to entrain the trash. The low speed fan is suitably locateddownstream of the upwardly projected air flow.

BRIEF DETAILS OF THE DRAWINGS

To assist in understanding the invention preferred embodiments will nowbe described with reference to the following figures in which:

FIG. 1 is a first embodiment of a sugar cane harvester having means forseparating billets of sugar cane from trash;

FIG. 2 is an enlarged view of the separating means of FIG. 1;

FIG. 3 is an alternate nozzle arrangement;

FIG. 4 is a second embodiment of a sugar cane harvester having means forseparating billets of sugar cane from trash;

FIG. 5 is an enlarged view of the separating means of FIG. 4.

FIG. 6 is a third embodiment of a sugar cane harvester having means forseparating billets of sugar cane from trash; and

FIG. 7 is an enlarged view of the separating means of FIG. 6.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings, like reference numerals refer to like parts.

Referring to FIG. 1, there is shown schematically a first embodiment ofa selfpropelled harvesting machine 1, specifically designed forharvesting sugar cane. In conventional manner the sugar cane tops arecut by a topper 2 and the cane is lifted by croplifter spirals 3. Aknockdown roller 4 levels the cane as it is cut by the basecutter 5. Thecut cane is conveyed by feed rollers 6 to choppers 7 that chop the canestalks into billets. The cane billets as well as trash, including topsand leaves, is transported in the direction of arrow 8 to a conveyor 9.A bed of cane, tops and leaves is formed on the moving conveyor.

The conveyor 9 is made of open mesh material that allows the passage ofupwardly projected jets of air 10 from nozzles 11. The conveyor moves inthe direction indicated by arrow 12. The nozzles 11 are narrow, elongatenozzles that produce a jet of air that is narrow with respect to thedirection of motion of the conveyor which extends across the width ofthe conveyor 9. As depicted in the embodiment of FIG. 1 there are twonozzles spaced along the direction of motion of the conveyor howeverthis is not essential for the operation of the invention.

A “narrow” jet (or air flow) in this instance is one where the effectivelength of the jet is substantially equal to the width of the separationzone and the width of the jet is no more than a fifteenth, andpreferably about a twentieth of its effective length. The effectivelength of the jet being the length of a single outlet extending for thefull width of the separation zone or the sum of a plurality of outletsdisposed in a row extending for the full width of the separation zone.In the present embodiment the outlet from nozzle 11 is substantiallyrectangular having a length of about 1000 mm and a width of about 35-45mm.

It has been established by the inventors that a “narrow jet” producingan air flow of approximately 50 m/s will agitate and lift the bed ofcane and trash so as to sort and segregate the moving bed into differentclasses according to the terminal velocity of each class. Lower terminalvelocity components, such as leaf and tops, are sorted to the top of thebed while higher terminal velocity components, such as cane billets,remain towards the bottom of the bed.

When the bed passes over the narrow jet, the bed rises or decompacts, isagitated by the air flow therethrough, and is broken up. Trash,including leaf and tops, is sorted to the top of the mat and some isblown away. The remainder of the trash is extracted by fans 13 operatingin suction ducts 14. The trash is ejected from the harvester 1 asindicated by arrows 15. The cane billets, now cleaned of trash, fallfrom the end of conveyor 9 in the direction of arrow 12 onto an elevator16. The elevator 16 is pivotable about a vertical axis 17, inconventional manner. The billets are discharged from the elevator at 18into an in-field bin (not shown).

Although the jets of air 10 are effective in removing trash there is noremoval of cane billets. It will be appreciated that the velocity of theupwardly projected jet of air is greater than the terminal velocity ofthe cane billet. The inventors postulate that a billet remains on theconveyor because a billet placed in the air jet, either lengthwise orcrosswise, falls out of the jet. Thus a billet is not entrained by theair flow and therefore is not ejected from the harvester with the trash.This is partly due to the velocity of the air jet relative to theterminal velocity of the billet and partly due to the shape of the canebillet relative to the shape and size of the air jet. The air jet shouldbe sufficiently narrow that a cane billet cannot be completely containedwithin the air jet and therefore entrained. The inventors have foundthat the air velocities described herein are suitable for cleaning sugarcane billets. If the invention is applied to other materials the airvelocities will change accordingly.

In contrast, a fan over the mat, sufficient to induce a flow ofapproximately 12 m/s will lift and remove the trash at the top of themat. The inventors have found that if the fan is placed above the matjust downstream of the elongate jet, as shown in FIG. 1, it will moreeffectively remove the trash from the cane bed. The combined action ofthe jet of air 10 and fan 13 forms a separation zone 19 in the bed 20,as shown most clearly in FIG. 2. The direction of travel of the cane bedis shown by arrow A. The separation zone 19 extends a small way upstreamof the jet of air 10 and a larger distance downstream. As mentionedabove, a stratification of the components of the bed occurs in theseparation zone such that the lighter components are at the top andavailable for removal.

FIG. 3 shows an alternate embodiment wherein the separation zone 21 isformed by a pair of air jets, 22, 23 and an extraction fan 24. The airjets are supplied from a nozzle 25 having two outlets. The fan 24operates in an extraction duct 26. As with the embodiment of FIG. 2 thebed of cane and trash 27 is raised and stratified. The lightercomponents at the top of the stratified bed are removed by theextraction fan 24. The double air jet forms a more extensive separationzone and allows for more complete stratification. In situations wherethere is a high trash content the single air jet embodient may notprovide sufficient sorting to achieve the desired cleaning of the canebillets and hence the two jet embodiment may be more suitable.

It will be appreciated that in some situations it may be appropriate toemploy three or more closely spaced nozzles to lift, agitate andseparate the cane and trash.

An alternate embodiment of a self-propelled harvesting machine is shownschematically in FIG. 4. As with the embodiment shown in FIG. 1, theself-propelled harvesting machine 1 is specifically designed forharvesting sugar cane. In conventional manner the sugar cane tops arecut by a topper 2 and the cane is lifted by croplifter spirals 3, aspreviously described. The knockdown roller 4 levels the cane which iscut by the basecutter 5. The cut cane is conveyed by feed rollers 6 tochoppers 7 that chop the cane stalks into billets. The cane billets aswell as trash, including tops and leaves, is projected in the directionof arrow 8 to form an unsupported bed of cane, tops and leaves.

Elongate nozzles 11 produce jets of air 10 that are narrow with respectto the direction of motion of the billets and trash and which extendacross the width of the unsupported bed. As shown in FIG. 4, there aretwo nozzles spaced along the direction of motion of the billets andtrash, however this is not essential for the operation of the invention.

As with the previous embodiment, the unsupported bed rises or decompactsas it passes over the narrow jets 10. Trash, including leaf and tops, issorted to the top of the bed and some is blown away. The remainder ofthe trash is extracted by fan 28 operating in duct 29. The fan 28 drawslow velocity air into the bottom of the duct 29 as indicated by arrows31. The trash is ejected from harvester 1 in the direction of arrow 30.The cane billets continue their trajectory onto elevator 16 and aredischarged from the elevator at 18, as previously described.

An enlarged view of the separation zone is shown in FIG. 5. As can beseen, the cane billets essentially follow a trajectory from the choppers7 to the elevator 16. The jets of air 10 act to fluidise the unsupportedbed of billets and trash thereby causing a separation of materialaccording to terminal velocity. The entraining air flow generated byextractor fan 28 acts throughout the separation zone 19 to draw awaytrash. This differs from the first embodiment where the entraining airflow acted adjacent the separation zone 19, as shown in FIG. 2 and FIG.3.

FIGS. 6 and 7 show a third embodiment of a sugar cane harvester whereinthe separation zone 19 is formed by three air jets 41, 42 and 43 and anextraction fan 28. The air jets 41, 42 and 43 are supplied from a nozzle25 having three rectangular narrow outlets. The fan 28 operates inextraction duct 29. As with the earlier embodiments the bed of cane israised and stratified. The lighter components at the top of thestratified bed are removed by the extraction fan 29. The triple air jetforms a more extensive separation zone and allows for more completestratification than in the single and double air jet embodiments ofFIGS. 2 and 3 respectively.

To ameliorate stratification within the separation zone 19, it ispreferable to vary the width of the rectangular outlets through whichthe air jets 41, 42 and 43 pass. In the embodiment shown in FIGS. 6 and7, the outlet associated with air jet 41 has a width of about 20 mm; theoutlet associated with jet 42 has a width of about 45 mm; and the outletassociated with jet 43 has a width of about 60 mm. By thus varying thewidth of the outlets, the penetration of the downstream air jet 43 intothe separation zone 19 is greater than air jet 42, which in turn isgreater in penetration than air jet 41. This graduates thestratification process which allows for more efficient removal of trashfrom the separation zone 19.

It will be appreciated that the second and third embodiments are able toutilise the primary extractor of conventional harvesters therebyminimising the effort required to retrofit the invention. Although adouble air jet is shown with the second embodiment and a triple air jetis shown in the third embodiment, it will be appreciated that a singleair jet, such as shown in FIG. 2, can also be employed. The principle ofoperation of the invention is the same in all three embodiments.

In each of the above embodiments, the suction ducts 14, 26 and 29 areopen at the front of the apparatus to draw additional air, as dictatedby the arrow 31 in FIG. 4, into the separation zone to assist in sortingand separating the components according to their terminal velocities.

Although the invention has been described in terms of its application tocleaning the trash from cane billets in a sugar cane harvester, it willbe appreciated that it is applicable to any situation requiring theseparation of components having different terminal velocities. In suchsituations, the components can generally be divided into distinctclasses having similar terminal velocities. The technique is moreeffective the more distinctly different are the terminal velocities ofthe respective classes of components being sorted. Effectiveness is alsogreater when each class of component being sorted is characterised bythere being minimal variation in terminal velocity amongst componentswithin the class. The invention may therefore be applied to separationof trash from such crops as potatoes, beans, carrots, fruit, grain, etc.

The inventors have found that when the invention is applied to a sugarcane harvester the effective separation rate can be increased becausethe separation zone is wider than with known separation techniques.

Throughout the specification the aim has been to describe the preferredembodiments of the invention without limiting the invention to any oneembodiment or specific collection of features.

What is claimed is:
 1. A self-propelled harvester comprising cutting andgathering means at a forward end of the harvester, chopping meansadjacent the cutting and gathering means for chopping harvested caneinto billets and trash, means for projecting said billets and trash ontoa conveyor means adjacent said means for projecting, said conveyor meansdefining a bed of billets and trash thereon and further defining aseparation zone, apparatus for separation of components of billets andtrash having differing terminal velocities, including means forproviding an upwardly directed air flow through said bed, said air flowacting to agitate, sort and separate said components according to aterminal velocity of each of said components, suction duct means abovesaid bed for entraining a class of said components sorted and separatedby said upwardly directed air flow including at least one narrow,elongate jet means extending substantially across said bed of saidcomponents, said means for entraining operating to entrain the trash outof the bed or separation zone.
 2. An apparatus as claimed in claim 1,wherein the jet has a width of no more than about one fifteenth of thelength of the jet.
 3. An apparatus as claimed in claim 1, wherein thewidth of the jet is about one twentieth of the length of the jet.
 4. Anapparatus as claimed in claim 2, wherein the jet has an outlet having awidth of about 15 to 65 mm.
 5. An apparatus as claimed in claim 2,wherein the jet outlet has a width of about 40 mm.
 6. An apparatus asclaimed in claim 4, including three spaced apart narrow upwardlyprojected air flows.
 7. An apparatus as claimed in claim 6, wherein atleast two of said three spaced apart air flows are of a different widthto each other.
 8. An apparatus as claimed in claim 7, wherein an airflow located further downstream along the bed has a larger width than anair flow located upstream along the bed.
 9. An apparatus as claimed inclaim 8, wherein said components are definable in classes wherein eachclass has a characteristic terminal velocity, and the terminalvelocities of the components in the class are distributed about a meanvalue which is the characteristic terminal velocity.
 10. An apparatus asclaimed in claim 9, wherein said suction duct means for entraining aclass of said components includes a low speed fan drawing an entrainingair flow away from the bed of components, said entraining air flowentraining low terminal velocity components.
 11. An apparatus as claimedin claim 10, wherein the suction duct means operates to entrain air flowthroughout and adjacent a separation zone.
 12. An apparatus as claimedin claim 11, wherein the upwardly projected flow of air and theentraining air flow act cooperatively to sort and segregate classes ofcomponents.
 13. An apparatus as claimed in claim 12, wherein theupwardly projected air flow has a velocity of between 20 m/s and 70 m/s.14. An apparatus as claimed in claim 13, wherein the upwardly projectedair flow has a velocity of between 30 m/s and 60 m/s.
 15. An apparatusas claimed in claim 14, wherein the upwardly projected air flow has avelocity of about 50 m/s.
 16. An apparatus as claimed in claim 12,wherein the entraining air flow has a velocity of between 2 m/s and 20m/s.
 17. An apparatus as claimed in claim 16, wherein the velocity ofthe entraining air flow is about 12 m/s.
 18. A self-propelled harvesteras claimed in claim 1, wherein the chopping means and the means forprojecting said billets and trash into said bed or separation zonecauses projection of the billets and trash into the separation zoneimmediately after chopping.
 19. A self-propelled harvester as claimed inclaim 18, wherein the conveyor means includes a belt of open meshmaterial.
 20. A self-propelled harvester as claimed in claim 1, whereinthe projection means forms an unsupported bed in the separation zone.21. The apparatus of claim 1 wherein the suction duct means isconfigured to draw additional air into the duct to assist in sorting andseparating the components according to terminal velocity.
 22. Anapparatus as claimed in claims 14, wherein the entraining air flow has avelocity of between 2 m/s and 20 m/s.